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Background: Picture descriptions are a commonly used tool in the diagnostic process of aphasias, including vascular as well as neurodegenerative disorders affecting language production. However, this widespread clinical use contrasts with the relative scarcity of empirical data exploring the role of different variables which can influence the results, particularly in cases in which the original procedure has been modified. This thesis addresses three areas in which such modifications need a much stronger empirical basis. Firstly, (1) the traditional default approach has been an oral picture description. However, a substantial group of patients, particularly those with neurodegenerative disorders affecting motor functions, cannot produce oral language. In such cases, an assessment of written language could offer a valuable alternative. Such a procedure would require, however, a systematic comparison between linguistic material collected in the spoken and written description. Another little-explored field is (2) the difference between traditional in-person versus remote testing. While remote testing has been possible for several decades, in the recent pandemic it became often the only available option. Research has been conducted on remote testing, but only for video-call testing settings. Automated online testing has not yet been assessed. Finally, in (3) the increasingly globalised world diagnostic material is used in different countries with diverse cultures and routines. Linguistic stimuli are translated (although not always adapted) but this is rarely the case for picture material. Therefore, the picture stimulus itself might be victim to misinterpretation if the patient is not culturally familiar with the depicted scene. However, the influence of the cultural familiarity of the picture material has not been addressed in research yet. AIM: The present thesis addressed the current gaps in research focussing on these three aspects: (1) the influence of production modality (spoken vs. written [handwritten vs. typed], (2) testing modality (in-person vs. video-call vs. automated online) and (3) picture stimulus (North American [traditional] vs. Indian) on the picture description task using a mix of literature reviews and empirical data. Method: A total of 100 healthy participants were tested (1) in two different production modalities, (2) in three different testing modalities and (3) with two different picture stimuli. The picture description was complemented by seven additional tests assessing naming, grammar, possible underlying dyslexia, concept formation, visual-spatial abilities and intelligence. The collected data were interpreted using an extended list of linguistic symptoms, statistical comparisons and linear models. Results: (1) Spoken picture descriptions were significantly longer, containing more words and sentences, whereas written descriptions were more concise, syntactically complex and lexically diverse. Unlike aphasic patients, healthy participants very rarely produced phonetic, syntactic or semantic errors. Isolated language functions and other cognitive abilities did not have a major influence on the picture description task. (2) The testing modality influenced the linguistic performance of the participants. Differences were more pronounced in the written task and could be traced back to differences between handwriting and typing. (3) The non- familiar scene produced a higher lexical diversity, but also a less complex syntax. Discussion: For clinical purposes but also research, (1) written picture descriptions should be considered for diagnosis as it is a more cost-effective method that can lead to conclusions of comparable relevance. Performance on tests of isolated linguistic domains and cognitive abilities do not have a significant influence on picture description tasks in healthy individuals. Therefore, picture descriptions cannot be used as a substitute for the assessment of isolated linguistic functions and cognitive abilities, or vice versa. (2) Equally, picture descriptions cannot be easily replaced by other tests, as they contain other types of information of considerable relevance. Remote testing is a useful tool that can be used in the diagnostic process, however, there are caveats that need to be considered before testing and interpretation. (3) A culturally non-familiar picture stimulus can lead to misinterpretation of the presented scene which might lead to false diagnoses. Therefore, the cultural origin of the stimulus needs to be taken into account when interpreting the results. Conclusion: Overall, all three examined modifications can be clinically feasible and useful. However, they cannot and should not be understood as identical to traditional methods, as they might have different limitations, but also offer different opportunities.

The overarching aim of this thesis is to explore the question of what role the knowledge and use of multiple languages plays in ageing. To answer this question two approaches were taken: first a natural history perspective on how languages change across the lifespan; second a training strategy investigating the effects of language learning in later life. Chapter 1 reviews the state of the art in terms of language learning in the third age. Chapter 2 outlines various methodological considerations and contexts of the presented empirical studies. Chapter 3 presents two empirical studies of natural history: (a) a completed study where multilingual adults across the lifespan participated in an autobiographical experiment investigating the role of language in relation to the vividity and intensity of memories and (b) on-going study exploring reported changes in the language abilities in later life. These studies reveal a dynamic role of language across the lifespan of multilinguals and the inescapable importance of individual variation and contextualised differences. The natural history investigation is followed by language learning classes across the lifespan where participants learned (a) Spanish for 2 hours 3 times a week across 4 weeks (24 hours total; Chapter 5), (b) written and spoken Mandarin Chinese 2 hours 2 times a week for 8 weeks (32 hours total; Chapter 6), or (c) Scots for 2 hours, 3 times a week for 3 weeks (18 hours total; Chapter 7). Apart from different languages being chosen, each chapter investigates a related aspect of the language. That is, the three selected languages function as an illustration of three general questions. In Chapter 5, Spanish was selected as the target language due to being one of the most popular foreign languages in the United Kingdom, though not typically taught in schools as is the case with French or German. Therefore, participants entering the course were complete beginners, regardless of age. This chapter concentrates on the different ages of participants and the relationships between learning success (as measured by quizzes) and the cognitive effects of language learning. Chapter 6 explores the question of modality (auditory and visual) of language learning and cognitive measures, benefitting from the unique feature of Mandarin Chinese in which the written and spoken language are dissociated to a much larger degree than in other living languages. Chapter 7 examines the issue of how the social status of a language might influence the learning process using Scots, which is debated in some circles as being a dialect of English rather than a language. These language learning studies were designed and analysed using a mixed methods approach, integrating both quantitative and qualitative data and analysis. In adopting a mixed methods approach to answering questions around the impact of language learning across the lifespan, the participant's opinions and experiences as well as cognitive variables are taken into consideration, creating a wholistic picture representative of lived experiences. Lastly, two primarily qualitative studies are presented in Chapter 7. One completed study which explores online language learning with older adults and provides recommendations for improving learning experiences, and another which is still in progress. Following from the practicalities of online learning with students in the third age, preliminary results are presented from a focus group study which then informed an international online survey looking at the experience of mixed age adult language learning classroom dynamics and practicalities from the point of view of teachers as well as learners. It is my hope that this thesis will make a two-fold contribution: (1) via the empirical findings of the individual studies and (2) in terms of exploring the importance of different methodologies and methodical considerations in answering diverse research questions.

The debate as to whether bilingual experience benefits individuals in terms of certain aspects of executive function has received much attention. The differences on cognitive performance between monolinguals and bilinguals have not been consistently replicated, which has raised concerns regarding the reliability and robustness of the cognitive effects associated with bilingualism. Given that bilingualism is a multidimensional, continuous, and dynamic phenomenon and varies with respect to many factors, the specific bilingual experience plays an important role in modulating the degree of bilingualism and, in turn, affects executive functions. Hence, identifying individuals' language experience is crucial for understanding the language control in bilinguals; importantly, it can shed light on the issue of the inconsistent evidence and identifying the possible reasons behind it. The first aim of this thesis is to understand the effects of specific language experience on executive functions (EF), particularly the components involved in language control, such as inhibitory control. The second aim is to explore the unsolved and lesser-investigated issues in the field of bilingualism research and to examine their impact on executive control in the context of bilingualism. These issues include: (i) inhibitory mechanisms for the reported inhibitory benefits associated with bilingualism (ii) pathways of language acquisition (i.e., language immersion versus instruction); and (iii) cognitive consequences of linguistic differences, such as linguistic distance and language script. EF performance in all of the studies carried out in this thesis was assessed by at least four non-linguistic cognitive tasks; namely, the Attention Network Task (ANT), the Number Stroop task, the Elevator subtests of the Test of Everyday Attention (TEA), and the Corsi Tapping Task (CTT), tapping into multiple dimensions of EF. The selection of the experimental tasks was based on the fact that the nature of language learning entails multiple domains, such as the visual (e.g., reading and writing), auditory (e.g., listening and speaking), and working memory (e.g., lexical and grammatical acquisition) domains. An additional arrow version of Simon task was included in the second and fourth studies. The first study investigates how language experience modulates EF in early adulthood Chinese learners of English. The results show that different aspects of language experience affect specific subcomponents of EF: language proficiency affects switching ability, disengagement of attention, inhibition in the visual domain, and auditory attentional switching, language exposure mainly affects switching ability and disengagement of attention, whereas the length of language use affects inhibition in both the visual and auditory domains. The second study examines the inhibitory mechanisms in young adult monolinguals and bilinguals and the role of language proficiency in modulating EF. The results show that bilingualism mainly influences interference suppression, but not response inhibition. Language proficiency turns out to differentially affect specific aspects of executive control and influence the emergence of group differences between monolinguals and bilinguals. The third study explores potentially different cognitive consequences of two pathways of language acquisition; namely, language instruction and language immersion. We examined EF longitudinally in young adult Chinese speakers learning English through instruction and immersion, respectively. The results suggest that overall the cognitive effects of L2 exposure are comparable in an instruction and immersion setting. However, subtle differences can be detected on specific cognitive tests such as auditory inhibition. The fourth study investigates whether linguistic differences extend to the cognitive domain as a result of language learning in Chinese and European populations. Specifically, the role of linguistic distance in spoken languages in modulating language control and executive control (Experiment 1), and how language script in written languages affects language acquisition and cognitive performance (Experiment 2). The results suggest that a larger linguistic distance is associated with better cognitive control; namely, general-domain executive control and inhibitory control. Moreover, language script plays a modulating role in cognitive performance: native Chinese speakers showed superior performance in visual attention tasks and mental rotation, while native English speakers obtained better performance in the auditory attention tasks. The results demonstrate that native language, linguistic distance, and script are significant predictors to EF, although the interaction with other factors, such as cultural differences and education systems, remains to be further studied. Taken together, this thesis focuses on the different aspects of language learning and bilingualism on different sub-components of executive functions in young adult populations. As to specific bilingual experience, we have investigated the less-explored factors, such as pathways of language acquisition (instruction vs. immersion), linguistic distance, and language scripts, and their impact on cognitive performance. Moreover, we have examined the effects of bilingualism on different types of inhibition mechanism (interference suppression vs. response inhibition) to specify the relationship between language control and inhibitory control. These findings contribute to our understanding of the key aspects of the bilingual experience that are responsible for the emergence of the cognitive effects of young adulthood bilingualism.

Early onset dementia is the gradual cognitive decline that interferes with independence in everyday activities, when it occurs in people younger than 65 years old (Fadil et al., 2009; American Psychiatric Association, 2013). The Edinburgh Cognitive and Behavioural ALS Screen (ECAS) was originally developed to assess cognitive and behavioural changes observed in amyotrophic lateral sclerosis (ALS) (Abrahams et al. 2014); as between 10- 15% of ALS patients develop frontotemporal dementia, and an additional 35% develop a milder cognitive impairment of frontotemporal dysfunction (Goldstein and Abrahams, 2013; Strong et al., 2017). The ECAS includes the domains of language, fluency, and executive functions for the assessment of ALS, but it also includes the domains of memory and visuospatial abilities to differentiate changes from other pathologies, such as Alzheimer's Disease (AD) (Abrahams et al. 2014). In addition, the ECAS includes a behavioural interview. In this thesis I explore whether the ECAS is a sensitive test to the types of cognitive and behavioural changes in people with early onset dementia without Amyotrophic Lateral Sclerosis (ALS). In the first study my objectives were: to investigate the relationship between the ECAS and the Addenbrooke's Cognitive Examination (ACE-III); to investigate the effects of age, education, and IQ on the ECAS, and create appropriate cut-off scores to determine abnormality. I assessed 80 healthy participants divided into four groups according to age and education. The ECAS and the ACE-III had a significant correlation indicating good convergent validity. IQ, followed by age, were the strongest predictors of the total ECAS score. While IQ predicted 46% of the ACE-III variance, it only predicted 24% of the ECAS variance. I created abnormality cut-off scores adjusted for age and education. This research was published in De Icaza Valenzuela et al. (2018). In the second study my aim was to determine the sensitivity of the ECAS to behavioural variant frontotemporal dementia (bvFTD) without ALS, AD, primary progressive aphasia (PPA) without ALS, posterior cortical atrophy (PCA) and mild cognitive impairment (MCI). I also validated the ECAS against a comprehensive neuropsychological assessment, and compared it with the ACE-III, for each diagnosis. We additionally performed a qualitative thematic analysis of the ECAS behavioural interviews to determine the differences in themes between the diagnoses of bvFTD and AD. The study included 16 people with bvFTD (without ALS), 32 with AD, 12 with MCI, 13 with PPA, 6 with PCA and 48 healthy controls. The ECAS was more sensitive than the ACE-III to detect bvFTD, AD, MCI and PPA; with equal sensitivity to detect PCA. The anterior functions (comprising executive, fluency and language scores) composite score was sensitive to bvFTD; while the posterior functions (comprising memory and visuospatial scores) composite score was sensitive to AD. The ECAS was able to detect cognitive impairment as determined by a comprehensive neuropsychological assessment in most of the patients. A cut-off of 4 or more behavioural domains affected differentiated well between bvFTD and AD, while different themes emerged between the groups in the qualitative analysis of the behavioural interview. Finally, for the third study my objectives were: to investigate the relationship between the ECAS and functional severity of dementia; to validate the behavioural interview of the ECAS with other behavioural screens used to assess FTD; and to determine whether the ECAS scores changed over time in bvFTD, AD, MCI, PPA, and PCA. For this purpose, I did a longitudinal study and analysed the correlations between the ECAS with the Clinical Dementia Rating Scale (CDR-FTLD), the Frontal Behavioural Inventory (FBI), and the Frontotemporal Dementia Rating Scale (FRS). I assessed 56 patients on the first assessment, 29 on the second assessment and 13 on the third assessment. The ECAS total score had good convergent validity with the CDR-FTLD severity classification, while the ECAS behavioural screen had convergent validity with the FBI, FRS and CDR-FTLD. I created an impairment cut-off score of 96 to differentiate the groups of questionable versus mild dementia based on the CDR-FTLD. The CDR-FTLD, FIQ, FBI, and FRS predicted 71.3% of the variance of the ECAS Total Score. The variance of the ECAS behavioural score was predicted 74.7% by the FBI, FIQ and age. FRS was the single variable to predict attrition by 20.4%. In our study there was no significant difference of ECAS scores between assessments. The ECAS proved to be a valid test to assess the cognitive and behavioural impairments in people with early onset dementia without ALS. It was more sensitive than the ACE-III at detecting dementia in most of the patient groups, with the exception of the PCA group where they had equal sensitivity. The ECAS had also equal sensitivity to detect bvFTD, PPA and PCA as an extensive neuropsychological assessment. It could therefore be used as a first assessment in early onset dementia clinics.

Although previous research has examined the effects of bilingualism on cognitive functions, specific biliteracy effects have not been investigated. This thesis looks at the effects of script on three major components of cognitive functions: executive control, mental rotation and hemispheric variance in distinguishing morphological markers. The research is composed of three studies, each focusing on a different aspect of cognitive functions. Study I compare's English monolinguals, Arabic monolinguals, English/Maltese bilinguals and English/Arabic bilinguals. The groups are tested using several executive control tasks (TEA and AX-CPT), concentrating on the fact that, like English, Maltese uses the Latin script, while Arabic uses its own. Maltese has the advantage of sharing a wide range of linguistic characteristics with Arabic, however is the only Semitic language to be written in the Latin script. Results revealed no significant effects of biliteracy on the executive control tasks related to inhibition and switching. In Study II, mental rotation is examined using three Corsi Block Tapping task; Forwards, Backwards and Rotated. The tasks were utilised in order to compare the English, Arabic, and Maltese groups on mental rotation. The results found that both Arabic speaking groups outperformed on the Rotated Corsi, while the English monolinguals and English/ Maltese bilinguals did not. This showed that while script does make a difference for mental rotation, it is an aspect of linguistic diversity, specifically the Arabic script, and not biliteracy. Further comparisons were done on Chinese monolinguals and bilinguals and led to the same conclusion, that the effects found on the mental rotation task are specific to the Arabic script. Further research on late Arabic learners revealed that the mental rotation effect is found after only one year of Arabic study. Study III utilised a visual and an auditory lexical decision task in order to investigate whether there are differences in hemispheric usage between the groups when making linguistic judgments. Previous research had suggested that Semitic languages, employ the use of both hemispheres of the brain in distinguishing morphological markers, whereas English readers rely on the left hemisphere (Ibrahim, Israeli, & Eviatar, 2007). The script differences between Maltese and Arabic helped determine whether the previous results were linked to the directionality of the script or the morphemes themselves. Results reiterated that both Semitic languages, Maltese and Arabic, showed no hemispheric preference in Maltese and Arabic respectively, however both groups and the English monolinguals showed a left hemispheric preference in English. The three studies report unique finding on an aspect of bilingualism that has not been examined, biliteracy. While the results did not show biliteracy effects on cognitive functions, linguistic diversity was shown to have an effect on both mental rotation and hemispheric variance in distinguishing morphological markers.

Posterior Cortical Atrophy (PCA) is a rare, progressive dementia characterised by visuospatial and visuoperceptual deficits (often with intact visual acuity), and a generally younger age of onset than typical Alzheimer's disease (AD) (Aresi & Giovagnoli, 2009; Caixeta, Taleb, Ghini, Dias Soares, de Melo Caizera & Vargas, 2013; Mendez, Ghjarania & Perryman, 2002). Patients with PCA typically present with fewer memory deficits, better verbal fluency, and better insight into their diagnosis compared with typical AD, although PCA and AD tend to converge clinically at advanced stages of disease progression (Lehmann et al., 2012). Despite being identified by Benson and colleagues three decades ago, there are still no widely agreed clinical diagnostic criteria for PCA and it remains relatively poorly understood (Benson, Davis & Snyder, 1988; Crutch et al., 2017). This PhD study was comprised of two phases. The initial screening phase involved a diverse battery of assessments with two main aims. First, this battery was intended to investigate the sensitivity and specificity of different screening tests in discriminating PCA patients (n = 6) from patients with other neurodegenerative dementias (n = 21) (typical Alzheimer's disease, frontotemporal dementia, Lewy body dementia, corticobasal degeneration, and primary progressive aphasia). The Modified Luria Alternating Square and Triangles (M-LAST) task achieved the highest sensitivity and specificity, closely followed by target cancellation and bisection tasks. The M-LAST task has not been reported previously in the assessment of PCA patients, but may have considerable potential for use in diagnostic settings. Similarly, an unusual variant of the bisection task (gap bisection, McIntosh et al., 2004) yielded the most impressive sensitivity for PCA. The secondary aim of the screening phase was to identify whether patients with other neurodegenerative diseases demonstrated deficits on the assessments which were specific to early visual function, as this is an area that has not been addressed previously in the literature. There was evidence of significant impairment for patients other than PCA on a number of measures. However, the most striking results from patients with dementias other than PCA were obtained on the second phase of assessment. The second laboratory-based phase aimed to more fully characterise the visuoattentional deficits associated with PCA (n = 5) and other dementias (n = 13), through the use of eye-tracking and motion-tracking technology. The PCA patients proved difficult to test under these conditions, as their visual impairments were so advanced and generalised that they appeared almost functionally blind on some tests. The most exciting novel results were obtained from patients with AD, in whom evidence of optic ataxia (misreaching to peripheral targets) was found for three of the four AD patients tested on a pointing task. These results, discussed in context with other recently published evidence (Gordon et al., 2018), suggest that screening for optic ataxia may have potential as a behavioural symptom potentially sensitive to early neuronal changes associated with AD. A systematic review of the literature was conducted in order to investigate the use of visual attention or visuomotor-specific assessments in the evaluation of patients with PCA. A case study was conducted of visual form agnosic patient DF, in whom recent evidence of optic ataxia has been found (Rossit et al., 2018; Hesse, Ball & Schenk, 2012, 2014). Strong evidence of optic ataxic-like pointing errors was observed in patient DF, with preserved grip scaling, implicit avoidance of obstacles and perceptual matching. An additional study on healthy participants was conducted in order to test whether attentional demands modulate performance on a visuomotor pointing task. The results indicated that increasing attentional demands led to optic ataxic-like pointing errors, thus the experimental manipulation appeared to serve as a model of optic ataxia in the healthy brain.

This thesis explored two main research questions, firstly investigating whether musical expertise offers a performance advantage in working memory for sequences of tones that vary in pitch, and secondly whether any advantage of musical expertise may be present in older as well as younger individuals. Previous research on working memory for tone sequences has reported that articulatory suppression interferes with temporary storage of verbal but not with tone sequences (Koelsch et al, 2009), suggesting a “tonal loop” within a musician’s working memory (Schulze, Zysset, Mueller, Friederici, & Koelsch, 2011) that complements the phonological loop for verbal material in musicians and non-musicians alike (e.g., Baddeley, 1986; 1992). The five experiments reported here explored detection of a pitch change between pairs of tone sequences with or without concurrent articulatory suppression or singing suppression. In Experiment 1, with pairs of auditory tonal (in a musical key) sequences to be compared, singing suppression impaired non-musicians significantly more than musicians, although both groups showed an impairment, whereas only non-musicians were affected by verbal articulatory suppression. In Experiment 2, conducted only with musicians who could read music, the first sequence of each pair was presented visually and the second sequence for comparison was presented aurally. Musicians were again impaired by singing suppression but not by articulatory suppression. For Experiment 3, for auditory atonal (no musical key) pairs of sequences, non-musicians performed at floor, and musicians were again significantly more impaired by singing suppression than by articulatory suppression. In contrast, for Experiment 4, only with musicians who could read music, for visually presented atonal sequences each followed by an auditory atonal sequence for comparison, musicians were significantly more impaired by articulatory suppression than singing suppression. These results suggest that for tonal sequences, musicians use their musical training and experience, coupled with subvocalised singing, but for atonal sequences, additional strategies involving phonological rehearsal may be used. Non-musicians may also rely on musical experience and subvocal singing for tonal sequences but seem to be unable to do so for atonal sequences. Results are consistent with the use by both musicians and non-musicians of a tonal loop for the rehearsal of tone sequences, which develops with musical training and may be used in addition to subvocal rehearsal. Previous research has suggested musical expertise may offer some protection against cognitive ageing (Hanna-Pladdy & MacKay, 2011; Amer, Kalender, Hasher, Trehub, & Wong, 2013). Experiment 5 in this thesis explored whether a lifetime of musical training and experience may offer the same advantages in old age for retaining tone sequences that had been found in Experiments 1 and 3 for younger musicians. This experiment also considered whether any advantage for older musicians on this task could be explained by the proposed “bilingual advantage” (e.g., Bialystok, Craik, Klein & Viswanathan, 2004), and what other aspects of cognition might be associated with tone sequence memory performance. A test battery was utilised with 74 older adults (60-80 years of age) to assess the influence of musical and language expertise, and cognitive abilities (attention, working memory capacity, self-reported prospective and retrospective memory) on the music-related pitch sequence comparison task from Experiments 1 and 3. Working memory capacity was found to predict individual differences in the ability to detect pitch changes between pairs of tone sequences, regardless of musical experience. Older musicians performed more poorly on the pitch change detection task overall than the younger musicians in the earlier experiments, but their performance on the task was significantly better than for age-matched non-musically trained peers who were close to floor for both tonal and atonal sequences, suggesting some benefit from a lifetime of musical experience.

A fundamental question in language research is the extent to which linguistic and cognitive systems interact. The aim of this thesis is to explore that relationship across new contexts and over the entire adult lifespan. This work centers on two branches of empirical research: the first is an investigation into the impact of later-life language learning on cognitive ageing (chapters 2-4), and the second examines the cognitive mechanisms underlying communicative perspective-taking from young adulthood into old age (chapter 5). The results of these chapters demonstrate that changes to one's linguistic environment can affect cognitive functions at any age, and similarly age-related changes to cognition can affect linguistic abilities, shedding light on the extent to which language and the brain are intricately connected over the lifespan. In the discussion (chapter 6), I consider how this work contributes new insights to the field, opening the door for future research to explore methods of improving cognitive abilities and linguistic behavior in old age.

Background: The human ability to adapt to extreme environments is fascinating. Research into this adaptation has been lacking in Arctic isolated teams because it has concentrated on Antarctic teams. The hazards of the poles often confine the researchers indoors with their colleagues, reducing their privacy. This deployment also limits their contact with loved ones at home. Subsequently, over the course of polar night, rates of anxiety, depression, irritability and sleep disturbance increase (Suedfeld & Palinkas, 2008). Often, the teams complain of cognitive impairments. The High Arctic’s distinctive feature is the polar bear. The presence of bears requires Arctic research station teams to handle fire arms for their personal safety. It also means that fire arms – which are highly restricted in the Antarctic – are ever-present and easily accessible at Arctic stations. This poses a unique psychological challenge for these teams which has not been well-researched. Methodology: This thesis is an original contribution to science in that it employs a mixed-methods approach combining phenomenological interviews, cognitive testing and mental health assessment via questionnaires with a team spending a year at the Polish Polar Station, Hornsund, Svalbard. The participants were ten of the eleven winter team members who spent the year between July 2015 and June 2016 at Hornsund (“Explorers”) and an age-/gender-/education-matched control group (“Controls”). They filled in the Symptom Checklist-90-Revised and the Profile of Mood States-Brief Version in July, September, January, April and June of that year. Cognitive testing was completed in September, January and June; it comprised the Figural Learning and Memory Test, the Sustained Attention to Response Task (SART), the elevator tasks of the Test of Everyday Attention (TEA) and the Raven Standard Progressive Matrices. The interviews took place at the same time as the cognitive testing. Results: The results showed that the most stressful time reported in the questionnaires was April 2016, just after the winter isolation had ended and the sun had risen again. The Explorers reported little subjective complaints about their cognition but they performed near-ceiling on the TEA while scoring far below their Controls on the SART. This implies a dichotomy between sustained attention and inhibition in the Explorers. Their lived experiences were shaped by a struggle to adapt to the other team members rather than by struggling to adapt to the hazardous environment. The environment was perceived as awe-inspiring. Over time, the Explorers shifted their view of the team from informal colleagues to a family which they did not choose to be a member of and then, to friends. Unanimously, other people were seen as the most difficult aspect of the mission. Conclusions: This thesis provides unique insight into a non-Anglo-Saxon Arctic wintering team: the conclusions suggest that participants should receive social training to get along better and be emotionally prepared. The findings can be implemented by my research partner, the Institute of Geophysics (Warsaw) to better select and prepare their future expeditions to Hornsund. Some of the insights such as the nature of the interpersonal stressors may be applicable to space missions.

The suggestion that bilinguals show enhanced cognitive control compared to monolinguals in certain aspects of executive function has received much contention. While this has been explained as a result of the extensive training in bilinguals having to manage the conflict that arises from their concurrently active langauges, others have argued that the superiority in executive control is attenuated when background variables such as immigration status, education and general cognitive ability is taken into account. This thesis was motivated by the general question: How is executive control influenced by differing bilingualism experiences? To this end, we compared attentional control performance in bilinguals and monolinguals on the Attention Network Test, the auditory Elevator task (Test of Everyday Attention), and the number Stroop task. The main aim of the thesis was to examine the role of two bilingualism factors: (i) interactional context (defined in the Adaptive Control Hypothesis, Green & Abutalebi, 2013), which pertains to how bilinguals switch between their languages, and (ii) linguistic distance, which refers to the extent of similarity between the bilingual's languages. The comparison between Edinburgh monolinguals, Edinburgh late bilinguals, Edinburgh early bilinguals, and Singapore early bilinguals as differentiated by their interactional context revealed better performance in bilinguals on two specific test components. Singapore bilinguals, who came from a dual-language and dense code-switching context, showed enhanced conflict resolution on the Attention Network Test, whilst Edinburgh late bilinguals, who were from a single-language context, were better on the Elevator reversal subtest tapping on attentional switching. The results thus suggest differential effects of interactional context on attentional control. We further compared task performance of bilinguals with related or distant L1-L2 combinations as defined by the linguistic and orthography overlap between their two languages. The data did not support a role of linguistic distance on attentional control. Edinburgh bilinguals studying an Indo-European language performed similarly to those studying the non Indo-European languages of Chinese and Japanese. In Singapore bilinguals, English-Chinese bilinguals also did not differ from English-Malay bilinguals on any of the test components. We supplemented the investigation by further examining if the factors of test-order and age could impact on how differences between monolinguals and bilinguals are exhibited. Our results suggest that monolinguals may show an improvement in attentional control after relatively short periods of engagement in experimental tasks, whilst bilinguals did not receive this boost. Test order may therefore partly explain the inconsistencies in literature regarding the claimed bilingual advantage. The comparison between older and younger adults also implied an effect of age. In young adults, bilinguals outperformed monolinguals on the Elevator reversal subtest of auditory switching, whereas the advantage shown in older bilinguals was on visual attentional orienting. The results across the various themes are reviewed and discussed with relevance to the current standing in the field, and suggestions for future research directions are put forth.

The daily practice of bilingual language control has been argued to affect both lexical processing and non-verbal executive control in bilingual speakers. On the one hand, bilingualism may slow down lexical processing in both languages. On the other hand, bilinguals have been said to show cognitive advantages compared to monolinguals, for example on inhibition and switching tasks. However, this ‘bilingual advantage’ is hotly debated, can often not be replicated, and language groups have been poorly matched on background variables in previous studies. Furthermore, I examined the reliability of the literature and found evidence for the existence of a publication bias (Chapter 3). This over-representation of positive studies compared to studies with null or negative findings hinders a reliable interpretation of the actual effects of bilingualism. The current thesis therefore aimed to examine possible effects of bilingualism on both lexical processing and executive control. Specifically, I investigated the effects of an understudied, but important feature of bilingualism: language use. Effects of bilingualism have been argued to be largest in older adults. Chapter 4 presents a study discussing inhibition and possible effects of age across various tasks. I show that inhibitory control and age effects depend on task-specific features, including the type of interference, type of stimuli, and processing speed. Next, I present a study (Chapter 5 and 6) examining the relation between bilingualism and both lexical processing and executive control in older adults. Importantly, bilingual and monolingual groups were matched on background variables including immigrant status. I furthermore compared a group of active to inactive bilinguals to assess effects of language use. On a lexical processing task, bilinguals had a disadvantage compared to monolinguals. This effect was modulated by language use, implying that not only language proficiency but also actual language use are needed to explain lexical effects of bilingualism. However, the non-verbal executive control tasks showed no consistent effects of bilingualism or language use on inhibition or task switching. Thus, this study did not replicate positive effects on executive control in older adults. Between-subject comparisons remain problematic as groups can never be matched perfectly. Furthermore, these designs cannot assess a causal effect of bilingualism. Therefore, I conducted another study using behavioural and EEG measurements to test for causal effects of language switching on task switching (Chapter 7). When young bilinguals completed a language-switching task prior to a verbal task-switching paradigm, they showed larger switching costs than after a monolingual naming task. However, this effect of language switching was not found for non-verbal task switching. Language switching may thus have a negative impact on verbal switching, but these effects did not extend to non-verbal executive control. Together, these studies suggest that bilingualism and language use affect lexical processing, but there was no evidence for effects of bilingualism and language use on non-verbal executive control in younger or older adults. In combination with other failed replications and the biased literature, this questions the reliability of cognitive benefits associated with bilingualism. However, executive control is not a unity and its manifestation depends on task-specific features. This task impurity, together with the degree to which participant groups are matched, may explain the inconsistency with which effects of bilingualism on executive control have been observed.

Background: Multiple sclerosis (MS) is a neurological disorder and the most frequent neurological cause of disability in young adults. 40-65% of MS patients experience cognitive difficulties (Bennedict et al., 2012), with problems in memory, attention and information processing speed being most frequently reported. However, visuoperceptual and language functions are much less studied in MS, but the few studies that looked into them (Vleugels, 2001; Grossman, 1995) have found prevalence of significant posterior deficits in MS. Up to today no study has investigated the domain-specificity of cognitive dysfunction in MS and its longitudinal progression. Aims: The primary aim of this project was to investigate the dimensionality of MS-related cognitive impairment longitudinally. The second aim was to determine the predictors of the observed longitudinal changes. The third aim was to investigate whether the participants themselves were aware of their cognitive changes, and what predicted the self-perception of change. Methods: To address these aims I followed a sample of MS patients and compared their performance on cognitive tests measuring five cognitive domains (verbal memory, visuospatial memory, processing speed, visuoperceptual and language) at baseline and at follow-up three years apart. Then I’ve composed separate models to explain the predictors first of the actual changes, and then of the perceived changes in performance. Moreover, as part of this project I have analysed pre-existing data to evaluate the instruments and optimized the baseline test battery for use in performing the followup assessments. Findings: I have managed to collect follow-up data on 82 MS patients and 23 matching healthy controls, acquiring high (76% and 79% respectively) recruitment rates. My MS sample (24% PPMS, 34% SPMS and 46% RRMS) was representable of the overall MS population. I found that deficits were seen in all cognitive domains (none were spared) and that new deficits were picked up sporadically, although with higher predisposition towards the information processing speed, visuoperceptual and memory domains. The new deficits showed the tendency to slowly accumulate, leading to development of major problems with longer disease duration. Interestingly it was found that even though the factors that influenced cognitive decline were specific for each of the cognitive domains, however, neurological disability, MS type and levels of depression were the most common predictors of change in cognitive functioning. I found that in general MS patients perceived longitudinal changes on the BRBN battery more accurately than on visuoperceptual and language tests, and the factors that played a role in the self-perception of change were executive dysfunction, neurological disability and MS impact. Implications: The results of this study add significant contribution to the field of longitudinal change in cognition in MS. Not only I explored the dimensionality of MS-related cognitive deficits, but also examined the factors that led to poorer performance, and the patients’ own perspective of their cognitive change. Moreover, with this project I have addressed common problems in the field of longitudinal research in MS – definition of normal variation in performance; the sensitivity of cognitive tests to pick up MS-related deficits; and heterogeneity of cognitive impairments in MS; - and I have used the performance of my own controls in attempts to account for all of that. I believe that this study will be of interest not only to those who specialize in cognitive functioning in MS, but also to those who question the methods employed in clinical research to define impairments and to account for individual differences.

Auditory comprehension, the ability to understand spoken language, consists of a number of different auditory processing skills. In the five studies presented in this thesis I investigated both intact and impaired auditory comprehension at different levels: voice versus phoneme perception, as well as single word auditory comprehension in terms of phonemic and semantic content. In the first study, using sounds from different continua of ‘male’-/pæ/ to ‘female’-/tæ/ and ‘male’-/tæ/ to ‘female’-/pæ/, healthy participants (n=18) showed that phonemes are categorised faster than voice, in contradistinction with the common hypothesis that voice information is stripped away (or normalised) to access phonemic content. Furthermore, reverse correlation analysis suggests that gender and phoneme are processed on the basis of different perceptual representations. A follow-up study (same paradigm) in stroke patients (n=25, right or left hemispheric brain lesions, both with and without aphasia) showed that lesions of the right frontal cortex (likely ventral inferior frontal gyrus) leads to systematic voice perception deficits while left hemispheric lesions can elicit both voice and phoneme deficits. Together these results show that phoneme processing is lateralized while voice information processing requires both hemispheres. Furthermore, this suggests that commencing Speech and Language Therapy at a low level of acoustic processing/voice perception may be an appropriate method in the treatment of phoneme perception impairments. A longitudinal case study (CF) of crossed aphasia (rare acquired communication impairment secondary to lesion ipsilateral to the dominant hand) is then presented alongside a mini-review of the literature. Extensive clinical investigation showed that CF presented with word-finding difficulties related to impaired auditory phonological analysis, while functional Magnetic Resonance Imaging (fMRI) analyses showed right hemispheric lateralization of language functions (reading, repetition and verb generation). These results, together with the co-morbidity analysis from the mini-review, suggest that crossed aphasia can be explained by developmental disorders which cause partial right lateralization shift of language processes. Interestingly, in CF this process did not affect voice lateralization and information processing, suggesting partial segregation of voice and speech processing. In the last two studies, auditory comprehension was examined at the single word level using a word-picture matching task with congruent (correct target) and incongruent (semantic, phonological and unrelated foils) conditions. fMRI in healthy participants (n=16) revealed a key role of the pars triangularis (phonological processing), the left angular gyrus (semantic incongruency) and the left precuneus (semantic relatedness) in this task – regions typically associated via the arcuate fasciculus and often impaired in aphasia. Further investigation of stroke patients on the same task (n=15) suggested that the connections between the angular gyrus and the pars triangularis serve a fundamental role in semantic processing. The quality of a published word-picture matching task was also investigated, with results questioning the clinical relevance of this task as an assessment tool. Finally, a pilot study looking at the effect of a computer-assisted auditory comprehension therapy (React2©) in 6 stroke patients (vs. 6 healthy controls and 6 stroke patients without therapy) is presented. Results show that the more therapy patients carry out the more improvement is seen in the semantic processing of single nouns. However, these results need to be reproduced on a larger scale in order to generalise any outcomes. Overall, the findings from these studies present new insight into, as well as extending on, current cognitive and neuroanatomical models of voice perception, speech perception and single word auditory comprehension. A combinatorial approach to cognitive and neuroanatomical models is proposed in order to further research, and thus improve clinical care, into impaired auditory comprehension.

What are the effects of non-balanced bilingualism on cognitive performance? And how do proficient, non-native speakers acquire and use lexical, syntactic and semantic information during sentence processing? Whilst there is growing research on these topics, there is no firm consensus on how to answer these questions. In the literature on cognitive effects of bilingualism, this lack of consensus has even resulted in radically opposing views and a heated debate. In this thesis, I seek to provide a balanced treatment of the literature and to address the above-mentioned questions by employing behavioral and neurophysiological paradigms. First, using a structural priming paradigm, I examine how proficient, non-native speakers of different native language backgrounds (Romance and Germanic) acquire lexically-specific syntactic restrictions of non-alternating verbs in English. Results from these experiments suggest that, although non-native speakers partially acquire lexically-specific syntactic restrictions, their knowledge is not native-like. Moreover, transfer from the first language does not seem to play a role in the acquisition of the relevant restrictions. Second, using Event-Related Potentials (ERPs) I examine whether proficient non-native Spanish-English speakers draw on different forms of semantic information such as relatedness and animacy incrementally during sentence comprehension. Results of these experiments suggest that, while relatedness facilitates processing (indexed by N400s) in both native and non-native speakers, effects of animacy are smaller in non-native speakers, relative to native speakers. Third, I employ a series of auditory attentional tasks and measures of lexical access and verbal fluency to assess cognitive functions in non-balanced bilinguals with different levels of language proficiency. Results show a bilingual advantage in inhibitory control and a non-significant trend towards bilingual better performance in attentional switching, and the groups exhibit similar performance on verbal fluency. Results of all the studies are discussed in the context of the existing literature on cognitive performance in bilinguals and accounts of language processing in native and non-native speakers and suggestions for future research are provided.

Background: Language impairment associated with Motor Neurone Disease (MND) has been documented since the late 19th century, yet little is understood about the pervasiveness or nature of these deficits. The common clinical view among healthcare professionals is that communication difficulties can be attributed solely to the motor speech disorder dysarthria. Recent literature raises the possibility of more central processing deficits. Impairments in naming ability and comprehension of complex grammatical constructs have been frequently reported in some patients with MND. However, there is now growing evidence of spelling impairment, which could suggest the contribution of a more phonologically based deficit. In addition, the close relationship between MND and frontotemporal dementia (FTD) raises questions about the connection between the language impairments seen in MND patients and those documented in patients with the primary progressive aphasia (PPA) syndromes associated with FTD. Aims: This thesis examines the nature of speech and language deficits in people with MND and the extent to which expressive communication impairment can occur above and beyond dysarthria. In particular, the study explores: i) to what extent these language impairments can be attributed to deficits in working memory, executive functioning and/or disease severity; ii) what spelling errors can reveal about the integrity of lexical, phonological and orthographic processing; iii) whether similar patterns of impairment can be seen in PPA syndromes; iv) the relationship between language impairment and bulbar onset; and v) the impact these findings have on clinical management of MND patients. Methods: MND patients from across Scotland with changes in speech and/or language were tested using a neuropsychological battery of experimental and standardised tests of naming, spelling, syntactic comprehension, prosody and phonological and orthographical awareness. Patients were also screened for levels of dysarthria, executive functioning and working memory deficits, and results compared to those of matched controls. Findings: As a group, MND participants performed significantly worse than matched controls on measures of naming, spelling, orthographical awareness, grammatical comprehension, affective prosody and verbal fluency, but not working memory. However, based on patterns of individual impairment, of which spelling impairment formed a distinctive marker, the patient group divided into dichotomous subgroups, with 44% of participants categorised as ‘linguistically impaired’, while the remainder displayed little to no impairment. Those participants identified as linguistically impaired did not differ significantly from other MND participants on measures of disease severity, disease duration or dysarthria severity, although significantly more bulbar onset than limb onset participants were linguistically impaired. Spelling error patterns were suggestive of deficits at both a lexical and sublexical level, and were comparable to those reported in PPA literature. These findings suggest that dysarthria may be masking linguistic deficits in almost half of dysarthric MND patients, and highlight the importance of multidimensional assessment of language for effective clinical management.

The present thesis set out to investigate how sensory modality and spatial presentation influence visual and auditory duration judgments in the millisecond range. The effects of modality and spatial location were explored by considering right and left side presentations of mixed or blocked visual and auditory stimuli. Several studies have shown that perceived duration of a stimulus can be affected by various extra-temporal factors such as modality and spatial position. Auditory stimuli lead to more precise duration judgments than visual stimuli and often last subjectively longer than visual stimuli of equal duration. The circumstances under which these modality differences occur are not clear yet. Recent studies indicated an interaction between temporal and spatial processing. Overestimation of durations was associated with right side presentation of visual stimuli, underestimation with left side presentation. However, the effect of spatial presentation has not been explored in the auditory temporal judgments. Furthermore, there is a debate concerning the mechanisms underlying processing of visual and auditory intervals with some researchers supporting the view that there is a central, amodal temporal mechanism and others arguing in favour of distinct, modality specific temporal mechanisms. The above issues were examined in a series of experiments using the duration discrimination paradigm. Processing demands where varied between experiments by varying the number of stimuli positions and the way that different modality trials were presented (mixed or blocked). Across all experiments we found no effect of location either in visual or auditory domain. However, in experiments in which different modality trials were intermixed, participants in the visual versions of the task tended to overestimate durations of comparison stimuli that were presented at different locations to the standard stimuli. In such conditions, visual stimuli were also judged to be longer than the auditory. However, when the location of the comparison stimulus was at the same side as the standard a reverse effect was observed. These findings call into question an influence of the position per se on temporal judgments as the visual duration judgments were affected rather by the change of the location. Auditory judgments were not affected by location manipulations, suggesting that different mechanisms might underlie visual and auditory temporal processing. Based on these results, we propose the existence of an error-correction mechanism, according to which a specific duration is added in order to compensate for the loss of time caused by spatial attention shifts. This mechanism is revealed under some circumstances (such as mixed modality) where it is over-activated, resulting into a systematic bias. This work has important implications for the contemporary research in time perception as it is shedding new light on the possible ways that a unified experience of timing arises from modally and spatially specific temporal mechanisms.

This PhD thesis examines the relationship between Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal dementia (FTD). ALS is a rapidly progressive neurodegenerative movement disorder characterized by muscle weakness, spasticity and abnormal reflexes. In a very small subset of patients (5-15%), ALS is associated with FTD. Furthermore, a larger subset of patients who do not suffer from overt dementia, develop subtle deficits in cognition and behaviour (up to 50%). The changes have mostly been observed in the domains of executive functions, language and behavioural functioning. These observations have led some researchers to propose a continuum of dysfunction between ALS and FTD, ranging from an absence of neuropsychological abnormalities to mild, subclinical changes to a profile consistent with a full-blown FTD-syndrome in ALS. FTD consists of three subsyndromes; the first ‘executive-behavioural’ type, frontal variant FTD (fvFTD), is predominantly characterized by behaviour abnormalities, difficulties with using strategies and social judgement. In contrast, the other two types mainly involve problems with ‘language’, including a central degradation of knowledge for words, objects, people (semantic dementia; SD) as well as complications with speaking, spelling and the sounds of language (progressive non-fluent aphasia; PNFA). The current study aims to explore whether the cognitive-behavioural deficits found in nondemented ALS-patients can be classified as subclinical forms of the first two FTDsyndromes, i.e. fvFTD and SD. In addition, the study further examined whether executive and language impairments co-exist or rather occur independently. To answer the research questions, a battery of neuropsychological tests was employed, adapted to patients’ speech and motor disabilities, as well as behavioural questionnaires. The data revealed there was evidence of both executive and language involvement characteristic of FTD, albeit to a subtle extent. ALS-patients showed deficits on a test of Theory of Mind (ToM). On this test, participants were asked to judge the thoughts and feelings of another, using the direction of eye gaze, a cue considered to be important for social interaction. Results indicated that ALS patients had difficulties with affective ToM, i.e. recognizing feelings of others, and this effect was not driven by perceptual or attentional difficulties. In addition, patients exhibited a subtle deficit with empathy as well as a range of behavioural abnormalities. Furthermore, ALS-patients showed abnormal performance on a complex multi-modal semantic association task which involved assigning the correct picture iii to the sound of an object. This central deficit emerged in the presence of normal audio-visual information processing and episodic memory functions. Moreover, a category-specific deficit for man-made objects was detected in patients. Individual case-analyses showed that various subsets of patients were impaired on the language and executive tasks. These analyses also showed that executive and language problems can occur independently as well as simultaneously in patients with ALS. In addition, analysis of individual cases revealed that some patients’ performance on the decision making tasks was similar to that found in patients with either orbitofrontal or dorsolateral dysfunction, while there was little if any evidence of a pattern of impairment similar to that seen with anterior cingulate dysfunction. The observed difficulties with social cognition and semantic processing indicate that executive and language problems, characteristic of the two FTD syndromes, can be detected in patients with classical ALS.

The present work introduces a synthesis of neocerebellar state estimation and feedforward control with multi-level language processing. The approach combines insights from clinical, imaging, and modelling work on the cerebellum with psycholinguistic and historical linguistic research. It finally provides the first experimental attempts towards the empirical validation of this synthesis, employing transcranial magnetic stimulation. A neuroanatomical locus traditionally seen as limited to lower sensorimotor functions, the cerebellum has, over the last decades, emerged as a widely accepted foundation of feedforward control and state estimation. Its cytoarchitectural homogeneity and diverse connectivity with virtually all parts of the central nervous system strongly support the idea of a uniform, domain-general cerebellar computation. Its reciprocal connectivity with language-related cortical areas suggests that this uniform cerebellar computation is also applied in language processing. Insight into the latter, however, remains an elusive desideratum; instead, research on cerebellar language functions is predominantly involved in the frontal cortical-like deficits (e.g. aphasias) seldom induced by cerebellar impairment. At the same time, reflections on cerebellar computations in language processing remain at most speculative, given the lack of discourse between cerebellar neuroscientists and psycholinguists. On the other hand, the fortunate contingency of the recent accommodation of these computations in psycholinguistic models provides the foundations for satisfying the desideratum above. The thesis thus formulates a neurolinguistic model whereby multi-level, predictive, associative linguistic operations are acquired and performed in neocerebello-cortical circuits, and are adaptively combined with cortico-cortical categorical processes. A broad range of psycholinguistic phenomena, involving, among others, "pragmatic normalization", "verbal/semantic illusions", associative priming, and phoneme restoration, are discussed in the light of recent findings on neocerebellar cognitive functions, and provide a rich research agenda for the experimental validation of the proposal. The hypothesis is then taken further, examining grammaticalization changes in the light of neocerebellar linguistic contributions. Despite a) the broad acceptance of routinization and automatization processes as the domain-general core of grammaticalization, b) the growing psycholinguistic research on routinized processing, and c) the evidence on neural circuits involved in automatization processes (crucially involving the cerebellum), interdisciplinary discourse remains strikingly poor. Based on the above, a synthesis is developed, whereby grammaticalization changes are introduced in routinized dialogical interaction as the result of maximized involvement of associative neocerebello-cortical processes. The thesis then turns to the first steps taken towards the verification of the hypothesis at hand. In view of the large methodological limitations of clinical research on cerebellar cognitive functions, the transcranial magnetic stimulation apparatus is employed instead, producing the very first linguistic experiments involving cerebellar stimulation. Despite the considerable technical difficulties met, neocerebellar loci are shown to be selectively involved in formal- and semantic-associative computations, with far-reaching consequences for neurolinguistic models of sentence processing. In particular, stimulation of the neocerebellar vermis is found to selectively enhance formal-associative priming in native speakers of English, and to disrupt, rather selectively, semantic-categorical priming in native speakers of Modern Greek, as well as to disrupt the practice-induced facilitation in processing repeatedly associated letter strings. Finally, stimulation of the right neocerebellar Crus I is found to enhance, quite selectively, semantic-associative priming in native speakers of English, while stimulation of the right neocerebellar vermis is shown to disrupt semantic priming altogether. The results are finally discussed in the light of a future research agenda overcoming the technical limitations met here.